The present invention relates, in general, to ultrasonic surgical instruments and, more particularly, to active load feedback control of ultrasonic surgical clamping instruments.
Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end-effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels and using a suitable end-effector, may be used to cut, dissect, or cauterize tissue. Ultrasonic instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer through the waveguide to the surgical end-effector. Such instruments are particularly suited for use in minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end-effector is passed through a trocar to reach the surgical site.
Ultrasonic vibration is induced in the surgical end-effector by, for example, electrically exciting a transducer which may be constructed of one or more piezoelectric or magnetostrictive elements in the instrument handpiece. Vibrations generated by the transducer section are transmitted to the surgical end-effector via an ultrasonic waveguide extending from the transducer section to the surgical end-effector.
U.S. Pat. No. 5,322,055 describes an ultrasonic surgical apparatus that includes a surgical instrument having a transducer for converting an electrical signal into longitudinal vibratory motion. The longitudinal vibratory motion is transmitted to an ultrasonic blade that is connected to the handpiece. An accessory is releasably connected to the handpiece to enable clamping of tissue against the vibrating blade to afford improved coagulating and cutting of tissue. In U.S. Pat. No. 5,322,055 scissors-like grips actuate a pivoted clamp jaw along one side of the ultrasonically vibrating blade to compress and bias tissue against the blade in a direction which is substantially normal to the direction of longitudinal vibratory motion. U.S. Pat. No. 5,322,055 is hereby incorporated herein by reference.
Hemostatic devices have been described in various instruments for cutting, cauterization, coagulation or tissue welding. Most of the devices used are either monopolar or bipolar, for example, bipolar forceps, monopolar or bipolar scissors, and cutting and coagulating devices. See, for example, U.S. Pat. No. 5,707,369 that describes a temperature feedback system for closed loop control of the tissue temperature induced by the surgical instrument wherein a function of the temperature is used to determine when coagulation of tissue has occurred to a desired degree.
Although open loop electrosurgical and ultrasonic instruments have been used successfully to control bleeding during surgical procedures, when such instruments are used, the primary control is the experience of the surgeon who responds to what is observed to be happening to the tissue as it is treated with energy. Often, particularly for endoscopic procedures, surgeons cannot readily see what is happening to the tissue. Also, the change in tissue properties due to the energy may occur so quickly so as not to afford time for the surgeon to react soon enough to turn off the energy to the instrument. As a result, the tissue treatment may not be as precisely controlled as may be desirable. Some problems that may occur include tissue charring, sticking of the tissue to the electrodes of electrosurgical instruments, and over or under treatment of the tissue.
There is a continuing need to improve the control of energy delivery to tissue and/or to determine when tissue treatment has reached an optimal or desired level. The amount of ultrasonic energy coupled into tissue is a function of the force applied to the tissue by the ultrasonic end-effector. Prior instruments, such as those described in U.S. Pat. No. 5,947,984 hereby incorporated herein by reference, have limited the maximum amount of force that a surgeon could apply to tissue. However this is a single maximum set-point, and does not actively control the force applied to the tissue below the set limit. In particular there is a need to provide a device and method for active control of ultrasonic instruments that must perform both cutting and coagulating functions.
The present invention meets the needs described above by providing a system including a force feedback system for use in surgical procedures. The force feedback system is a closed loop arrangement that can modulate the force applied to tissue from a surgical instrument. A generator produces an electrical signal, which has a load parameter indicative of generator load. A load parameter may be, for example, current, voltage, impedance or temperature. A surgical instrument is electrically connected to the generator. The surgical instrument includes a handle that includes an actuating lever, and an end-effector located at the distal end of the handle. A force responsive element is operatively coupled to the actuating lever and the end-effector, wherein the force responsive element is adapted to alter a force on the end-effector in response to the electrical signal from the generator.